The objective of this program is to determine and quantify and temporal and spatial nature and degree of histopathologic alterations of normal brain after treatment with clinically relevant levels of 192 Iridium interstitial brachytherapy in combination with interstitial 2450 MHz hyperthermia. The proposed program will deliver 5000 rad (100 rad/hr for 50 hr), measured at a point 2 mm from the source, and 45 degree C for 45min., measured at the microwave antenna, to the brain of Yucatan mini swine. Experimental controls will include animals treated with radiation alone, heat alone and sham controls. Analysis of temporal changes will be made in animals sacrificed at 1 week and 1, 3, 6, and 12 months following treatment. Treatment levels at increasing radial distances from the source of radiation and/or heat will be determined by computer predicted isodose distributions (for interstitial brachytherapy) and empirical isotherm distributions (for interstitial hyperthermia). Histopathologic alterations will be determined at specific treatment levels (decreasing doses at increasing radial distance from the source) and correlation made in order to identify the dose related region of brain tolerance. This study will provide important data fundamental to determining the dose-effect-time temperature response relationships of normal brain following hyperthermia and radiation therapy.